Interferons are glycoproteins whose synthesis is induced in various animal cells upon infection by any of a large variety of viruses. They are released from the producing cells, are attached to other cells and impair in these the replication of a large variety of viruses. We are studying the molecular basis of this impairment. Many of our studies are performed with mouse Ehrlich ascites tumor cells, mouse L fibroblasts and reovirus, a virus with a segmented double-strained RNA genome. Extracts from interferon-treated cells (S30 INT) differ from extracts of control cells (S30C) in various biochemical charcteristics. 1. Viral mRNAs are degraded faster in S30INT than in S30C but only if the extracts are supplemented with double-stranded RNA and ATP. We are purifying and characterizing the endonuclease system catalyzing this degradation. 2. Double-stranded RNA promotes the phosphorylation by ATP of several proteins in S30INT and only to a much lesser extent in S30C. We are purifying and characterizing the protein kinase(s) catalyzing these reactions. We are also attempting to elucidate the role of double-stranded RNA in the activation of the enzyme(s). Other studies in the laboratory concern the effect of interferon treatment on viral RNA synthesis, viral RNA turnover and viral mRNA translation in interferon-treated intact cells.